Washington: The United States is doing little to defend the planet against potentially devastating asteroids and is not doing the basic searches that Congress has ordered, according to a report.

While most of the really big and obvious threats are being found, almost nothing is being done to find the smaller objects that are arguably a more likely threat, the strongly worded report from the National Academy of Sciences said.

"It means we are not looking for the small ones which can cause huge damage on earth," astronomer Mike A`Hearn of the University of Maryland, who helped chair the committee that wrote the report, said in a telephone interview.

"Why has nothing been done? I don`t know," added A`Hearn, who was principal investigator of NASA`S 2005 Deep Impact mission to knock open the comet 9P/Tempel.

He said it was not clear whether the administration of President Barack Obama, who has declared his support for science but is struggling with an economic downturn and budget deficits, would work any harder to do more.

The United States spends about $4 million a year looking for near-Earth objects, or NEOs, that might come too close. In 2005, Congress ordered a broader survey to find 90 percent of near-Earth objects 140 meters (460 feet) in diameter or greater.

Something this big could cause enormous regional damage.

But Congress has not funded this search and neither former President George W. Bush nor Obama have asked for it.

A`Hearn`s committee made several recommendations.

"They are all expensive compared to what we are spending now. Compared to other things the country is spending money on they aren`t expensive," he said.

"The minimal sensible program is probably two and a half times larger than the current program," he added.

To simply do what Congress asked in 2005 would likely cost $4 million, A`Hearn said.

And less than $1 million is being spent to study what could be done if it looked like something destructive was headed toward the Earth, the report found.

At the very least, civil defense measures should be planned, A`Hearn said. "For an object up to 50 to 75 meters (164 to 246 feet), civil defense is the right answer. You simply evacuate the area where it going to hit," he said -- although he noted how difficult it is to evacuate areas where hurricanes are bearing down.

An object that size would create the equivalent of a nuclear explosion in the sky, blowing down trees, buildings and killing animals and people underneath it.

Larger, more dangerous comets or asteroids could be deflected or blown up, but it would take years of planning to do so. And no one has systematically looked at the diplomacy and politics that would be involved.

"It wouldn`t be a dramatic change in defense department budget to develop the capability to destroy near-Earth objects. On the other hand, there may be other countries that might not trust us to do it right," A`Hearn said.

Or a program could be interpreted as a weapons program and a threat, so diplomacy would be needed to ensure international cooperation and acceptance, A`Hearn said.

A`Hearn said he was not sure if Obama`s declared support of science would extend to this program, or whether new space agency administrator Charlie Bolden would fight for it.

"The administration and the NASA administrator say nice words about science but it takes a while to implement things," he said.